On permanent display in the Royal Armouries’ collection at Fort Nelson, Hampshire are two huge, steel pipes bolted together and projecting high into the air. They’re enormous, big enough for someone to crawl through.
These giant cylinders are one of the few remaining pieces of a contender for one of the most audacious pieces of engineering ever designed: a “supergun” called Big Babylon, which could have fired satellites into orbit from a 156m-long barrel (512ft) embedded inside a hill.